This invention relates to a means and method for measuring and controlling smoke from an internal combustion engine, and more particularly to a means and method for measuring soot emissions from a diesel engine which can also be used for adjusting at least one (1) parameter of the engine to control soot emissions.
With modern technology and electronics, many of the components and running conditions of an internal combustion engine can be controlled more accurately than with previous mechanical systems. For example, the control of the air/fuel ratio, spark timing, fuel injection timing and pulse, and other adjustable factors of engine operation are greatly facilitated through the use of electronic components and electronic computers. However, in order to accurately sense the running of the engine and the combustion during each combustion cycle, it is necessary to provide a sensor that is directly positioned within the combustion chamber or in proximity to it and which senses the actual combustion conditions in the chamber.
It has been understood that knocking can be determined by an optical sensor that operates within the combustion chamber and which senses the luminosity of the gases in that chamber. A wide variety of knock detectors have been proposed that employ such sensors. It has also been shown that the luminosity of soot in a diesel combustion chamber is related to black smoke (Bosch smoke) or soot emissions from a diesel engine. See for example, "Soot Formation and Oxidation in Diesel Engines" by H. Hiroyasu, M. Arai and K. Nakanishi.
However, the inventors have discovered that a luminosity signal indicative of soot in a combustion chamber can be measured using gain independent parameters and the measurements used to develop an equation which correlates the actual Bosch smoke being emitted from the exhaust with a predicted Bosch smoke value resulting from the luminosity signals. The inventors have also found that the Bosch smoke being emitted from the exhaust of an engine can be measured directly from the output signals of a luminosity probe. The inventors have also discovered that these luminosity signals and Bosch smoke measurements can be used in connection with an engine control loop for controlling Bosch smoke emissions by adjustment of one or more of the engine parameters so as to maintain a desired luminosity and thereby to maintain a desired level of Bosch smoke emissions. The inventors have also found that such measurement and control can be done independent of variations in engine parameters such as engine speed, fuel delivery, air/fuel ratio, intake manifold pressure, intake manifold temperature, compression ratio differences, injection system variations and fuel characteristics.
Although the measurement and control of exhaust smoke is important in all internal combustion engines, it is particularly important on diesel engines where the smoke and particulate emissions are high compared to such emissions in spark ignited engines. It has also been shown that under high smoke conditions (rich air/fuel ratios) Bosch smoke emissions and particulate emissions are the same but that these emissions differ under low smoke operation. The measurement and control of exhaust emissions is also important from an emissions standards standpoint. The use of the diesel engine in the future will be largely dependent on whether it can meet future emissions standards. For this reason, the inventors have performed their studies on a diesel engine, although the invention is applicable to spark ignited engines operating under high smoke conditions and stratified charge engines as well.
It is, therefore, a principal object of this invention to provide a means and method for measuring smoke emissions from an internal combustion engine on the basis of the luminosity of soot detected in the combustion chamber.
It is a further object of this invention to provide a means and method for measuring smoke emissions from an internal combustion engine independent of variations in engine parameters.
It is a still further object of this invention to provide a means and method for measuring smoke emissions from an internal combustion engine on a cycle to cycle and on a chamber to chamber basis. An average luminosity signal can also be obtained to measure smoke emissions over a period of several cycles.
It is yet a further object of this invention to provide a means and method not only for measuring smoke emissions in an internal combustion engine, but for controlling such emissions as well on the basis of the luminosity signals.
Engine sensors have been proposed that will detect the actual luminosity of the gases within the combustion chamber. A wide variety of patents illustrating and describing the use of such sensors have issued including the following:
U.S. Pat. Nos. 4,358,952; 4,369,748; 4,377,086; 4,393,687; 4,409,815; 4,412,446; 4,413,509; 4,419,212; 4,422,321; 4,422,323; 4,425,788; 4,468,949; 4,444,043; 4,515,132
For the most part, these patents disclose arrangements wherein the sensor is utilized to sense only total luminosity and to equate the luminosity signal to a knocking signal.
However, the inventors have discovered that the luminosity signal from a particular type of sensor used to detect soot within the combustion chamber, can be employed to directly measure soot emissions, and that this signal can further be used to adjust the engine parameters to control such emissions.